The present invention relates to fiber web processing and more particularly to devices for severing air laid webs.
In the formation of web sections from air laid webs, any permanent compression of the fibers will result in increased wickability, or preferential absorptivity along the compressed fibers due to the reduction in effective capillary radius of these fibers. This result may be most disadvantageous in the formation of diaper web sections since liquid migration will be along the line of densification. If this line occurs at an edge, as where the section is cut with a knife edge, there is a strong tendency for any liquid coming into contact with the densification line to be drawn into and concentrated at the edge. Accordingly, there exists a need for web-tearing devices which are capable of partitioning a web into segments without producing undesirable lines of densification. Both the commonly assigned Shepherd application, U.S. Ser. No. 377,372, filed July 9, 1973, and the present specification disclose devices which tear a web to form sections without creating densification at the tear line.
The aforementioned Shepherd application discloses apparatus for tearing an intermittently fed web wherein a pair of juxtaposed opposing jaws operate transversely on a web to form sections. Each pair of jaws consists of a first jaw and a second biased hinged jaw so that after the jaws grip the web, the first jaws hold the web and the second jaws are displaced from their juxtaposed position, thus tearing the web transversely. The apparatus and method of the present invention is directed to severing web sections from a continuously fed web at high production rates.
German Patent No. 1,252,050 to Hesser shows a device for separating cardboard sections defined by lines of weakening from a continuous strip of cardboard. The section to be severed from the strip is held between a rubber bar and an underlying roller while the rest of the continuous strip is moved rearwardly by the action of a single, slidably-mounted segment of the underlying roller. In contradistinction thereto, in the present apparatus a continuously moving web is fed between two opposed rotatable pairs of web engaging jaw members and is gripped by the trailing set of jaw members while the leading set of jaw members is accelerated away from the trailing set to sever a web section and to move the severed section away from the web.